[Andreas97]

I have a heat exchanger in a smaller room which I want to simulate conductive heat transfer between the water in the pipe of the exchanger and the convective heat transfer between the surrounding air and the exchanger.

Default fluid is set to air and to define water in the pipe of the exchanger I use insert fluid subdomain and clicking on the inlet of the pipe and choosing water with a specified temperature. Do I have to choose a flow velocity in X, Y, Z-direction or is it enough to define the inlet volume flow with a boundary inlet condition?

My problem is very similar to the one in the linked video below, but I can't see if he has defined any velocity in the Z-direction in the fluid subdomain.
https://www.youtube.com/watch?v=bNWhaitBPqE

[native]

If you don't want to give a certain velocity distribution, volume flow rate should be enough. Keep in mind to set a corresponding outlet boundary condition, e. g. ambient pressure.

You have to activate "Gravity" in the simulation settings to get free convection at the outside of the heat exchanger.

[Andreas97]

Originally Posted by native

If you don't want to give a certain velocity distribution, volume flow rate should be enough. Keep in mind to set a corresponding outlet boundary condition, e. g. ambient pressure.

You have to activate "Gravity" in the simulation settings to get free convection at the outside of the heat exchanger.

Thanks! This is what I have done